1. Field of the Invention
The present invention relates to an image pickup device and, more particularly, to an image pickup device which uses a solid-state image pickup element and has a wide dynamic range.
2. Related Background Art
Conventionally, there have been proposed a large number of inventions related to widening of the dynamic ranges of image pickup devices using solid-state image pickup elements. As an example of these conventional techniques, there is a method of dividing one field period of a television signal mode into a plurality of periods and adding signals stored in the individual divided periods. This prevents saturation of the stored electric charge, thereby widening the dynamic range.
As another example, there is a method in which long and short different charge storage times are set, and, if overflow occurs in the long storage time, the corresponding signal is removed, and the signal stored in the short storage time is output, thereby preventing overflow and blooming.
In the former example, however, noise components are mixed because signals are read out a plurality of number of times, and this degrades the S/N ratio, leading to a decrease in the dynamic range. The latter example has a problem of complexity in the stored gate signal. In addition, the storage time is shortened in an overflowed pixel unlike in other pixels, and the charge amount of this pixel becomes smaller than those of other pixels which have not overflown.